OKLAHOMA CITY - Against the team with the NBA’s second-best record - a team that recently had two players combine for 91 points in a game - the Celtics will try to earn some type of momentum and respect tonight before they hit the All-Star break.

This has been an embarrassing stretch for the Celtics, who have lost twice to the Pistons and dropped a listless decision to the Raptors. And against championship contenders such as the Mavericks, they are either unable or unwilling to compete.

Monday night in Dallas, it was the former. The Celtics officially went from banged up to crippled when Jermaine O’Neal and Chris Wilcox left the 89-73 loss in the same quarter with injuries. It is uncertain whether either will play tonight against the Thunder, but Kevin Garnett is expected to return from a two-game absence because of a family matter.

A team that had won nine of 10 games and seemingly distanced itself from the .500 mark now stands one game below it and must face the wildly athletic and high-scoring Thunder - perhaps the worst matchup for a slow-footed, depth-challenged Boston team.

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Still, there remains a confidence in the locker room. Though they realize their chances of nabbing the No. 1 seed in the Eastern Conference are highly unlikely, the Celtics are only five games behind the third-seeded Magic, a team they have already beaten twice.

The question is whether the Celtics are able, in their current state, to compete with the conference elite, especially with a road-heavy schedule for the final 35 games.

Coach Doc Rivers maintains that great things are possible, but health is mandatory.

“The season’s long, obviously, and who wants to be a game under .500 going to Oklahoma in the last game before the [end of the] road trip?’’ Rivers said. “Having said that, we get Kevin back, which is huge for us, with Paul [Pierce] and Ray [Allen].

“After the break, then Brandon [Bass] will be back and we’ll be back, and we’ve got to make a run.’’

The lockout has affected players’ health this season far more than most coaches and observers expected. No Celtic has played in all 31 games; Garnett is the lone front-line Celtic to not miss a game with an injury.

Pierce was hobbling at the beginning, Rajon Rondo missed eight games with a sprained right wrist, Allen sat out with a sprained ankle, and O’Neal is constantly battling different ailments.

And the most overshadowed injury is to Bass, one of the young Celtics, who is sitting out to allow his sore left knee to heal.

The Celtics have been unable to establish any personality and consistency because of subpar efforts and injuries. That has to change if they are going to be a legitimate contender.

Asked if this is a championship-caliber team, Allen said, “It is, in my opinion.

“You go into it very optimistic, prepare for Oklahoma City, don’t worry about what’s been ailing us because we have to clean that up.

“I tell these guys all the time, from the first to the fourth quarter, we have to make sure that we don’t make the same mistakes and we have to improve.’’

Quality big men are difficult to find, so the Celtics are unlikely to replace O’Neal or Wilcox unless their injuries become significant. Wilcox (groin) said he will try to play tonight, while O’Neal did not address reporters.

Rivers said the injuries are so prevalent now that he doesn’t bother to ask head trainer Ed Lacerte about the extent of them.

But with more than half the season remaining, there is no hint of relenting or preparing for the long-term future. The Big Three will remain in Boston, for now.

“You’ve got to hold the fort for as long as you can until you get bodies back,’’ Rivers said. “Win a game here or there, get healthy and make a run.

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